A vehicle incorporating powertrain referred to as a hybrid system has been developed and put into practical use. The hybrid system is a combination of an internal combustion engine (for example, a known engine such as a gasoline engine, a diesel engine or the like may be used) and an electric motor. Such a vehicle incorporates electric devices such as a secondary battery for driving an electric motor for traveling purpose, an inverter, a DC/DC converter and the like. The secondary battery is discharged and charged by a chemical reaction, which is associated with heat generation, and therefore the secondary battery must be cooled. The inverter and the DC/DC converter must also be cooled since their power devices generate heat.
Such a secondary battery is in some cases arranged between the rear seat of the vehicle and the luggage room. The secondary battery is arranged in a duct-like casing that forms an air passage. On the upstream side, in terms of air flow, of the secondary battery in the casing, between the battery and the rear seat, a cooling fan that generates cooling air for cooling the battery is arranged. Since the upstream-side end of the casing communicates with the cabin (specifically, opens to a rear package tray), the secondary battery is cooled by the air in the cabin.
In some cases, the inverter, the DC/DC converter and the like may be integrally incorporated as an electric device referred to as a PCU (Power Control Unit) in the vehicle. The PCU is stored in the engine room and cooled by air or water as a medium.
Since the secondary battery or the PCU must be incorporated in the hybrid vehicle in addition to the engine, the secondary battery or the PCU must be reduced in size for improved suitability for such incorporation. Japanese Patent Laying-Open No. 2004-306726 discloses a cooling structure for a battery pack including a battery and electric devices such as a DC/DC converter, a system main relay and the like, which excellently cools both the battery and the electric devices without increasing the size of the battery pack. The cooling structure is for cooling a battery pack for a vehicle, which is constituted of a battery portion having a battery module, and an accessory portion configured to include electric components associated with the battery portion. The cooling structure includes a flow passage for allowing a cooling medium to flow in parallel with the battery portion and the accessory portion, and a cooling fan for allowing the cooling medium to flow through the flow passage.
According to the battery pack cooling structure, the cooling fan allows the cooling medium to flow through the flow passage in parallel with the battery portion and the accessory portion, and therefore the battery module and the electric components can both be cooled efficiently and be reduced in size.
However, the battery pack cooling structure disclosed in Japanese Patent Laying-Open No. 2004-306726 cools both the battery module and the electric components using the fan that is shared by the battery portion and the accessory portion included in the battery pack. Accordingly, even though the battery pack including the cooling fan (and the battery module and the electric components) may be reduced in size, it is not possible to appropriately respond to a cooling request from one of the battery module and the electric components.